As is widely known, communicating with manned and unmanned submersibles at sea presents unique challenges. The very reason for the effectiveness of these stealthy platforms --the relative opacity of the ocean depths to electromagnetic radiation--makes real-time communication with submersibles the most difficult command and control problem facing the world's navies today. In fact, it is the case that the desire for real-time, continuous, and reliable two-way communication between submersibles and other communication nodes is at odds with the exigencies of submarine operations. Notwithstanding, a wide variety of communications systems have been developed to help ameliorate the difficulties which characterize submarine communications. These systems aggregately use the full communications frequency spectrum, from super high frequency (SHF) communications systems between submersibles and satellite relay nodes to extremely low frequency (ELF) communications systems which use land-based antennas that are several miles in length. In addition to the more conventional communications systems, recent developments in blue-green laser technology have made laser communications with submersibles feasible
It is the case, however, that no single communications system has yet been developed that is without significant shortcomings. For example, communications systems which permit the submersible to remain covert by communicating at relatively deep water depths, such as laser communications and ELF, also have inherently low data transmission rates. Thus, only a limited amount of data per a given time period may be transmitted via these systems. Moreover, it is generally the case that due to transmitter size requirements, systems such as ELF can support only one-way communication to the submarine. On the other hand, high frequency (HF), ultra high frequency (UHF), and super high frequency (SHF) communications are capable of supporting real-time, high data rate, two-way communication between submarines and surface vessels, aircraft, or satellites. Unfortunately, in order to employ such systems, the submarine typically must operate close enough to the ocean's surface to permit raising a communications mast or antenna above the surface of the water. This requirement in turn restricts the submarine's operating envelope and reduces the submarine's acoustic sensing capabilities as well as its overall covertness, all of which factors deleteriously affect submarine operations. Moreover, permitting a submarine to remain deep while communicating is important even when covertness is of little concern. For example, an unmanned research submersible that can communicate with off-hull nodes while remaining deep accordingly avoids undue interference with its operating schedule or routine.
Several communications systems have been developed which attempt to exploit the advantages of real-time, relatively high data rate HF and UHF communications, while permitting the submarine to remain relatively deep while communicating. Foremost among these systems are communication buoys. Communication buoys are devices which may be pre-programmed with a message, then deployed by the submersible to float to the water's surface in order to transmit the pre-programmed message to a satellite or other communications node. Some of these devices are additionally equipped with a small transducer, which gives the buoy the capability to acoustically re-transmit message to the submersible that are received by the buoy on radio frequencies. In any case, it is evident that such devices must incorporate an appropriately oriented RF antenna in order to transmit and receive messages over HF and UHF frequencies. Moreover, the antenna of such a device must be sufficiently large to be functionally effective. On the other hand, many such devices may be required by the submersible over a period of time. Therefore, the antenna of the device must be configurable to facilitate storage of several of the devices in the relatively small and limited storage spaces of a submersible. To meet these requirements, some communication buoys have been proposed that have an antenna which is movable between a shortened and a lengthened configuration, similar to an automobile antenna. Like many remote-controlled automobile antennas, the antenna associated with several of these types of communications buoys are telescoped by a motor and drive screw actuator. It will be immediately recognized, however, that such an actuator is inherently relatively heavy and expensive, both of which attributes are fundamentally incompatible with the need for deploying a large number of reliable, yet light weight and buoyant, communications buoys.
Accordingly, it is an object of the present invention to provide a deployable antenna for underwater launched communications buoys which is sufficiently large to be functional as a UHF antenna. It is another object of the present invention to provide a deployable antenna for underwater launched communications buoys that is sufficiently compact to permit storage in a relatively small area. Yet another object of the present invention is to provide a deployable antenna for underwater launched communications buoys which is buoyant and which may be oriented to maximize communications connectivity across the antenna. Still another object of the present invention is to provide a deployable antenna for underwater launched communications buoys that is relatively inexpensive and cost effective to manufacture.